Mars and Venus are much further apart than previously thought - and we're not talking about planets...

In research published on Wednesday, three European psychologists, using a new model for analyzing personality differences between men and women, claimed the gap between the genders has been sorely underestimated in previous studies.

"The idea that there are only minor differences between the personality profiles of males and females should be rejected as based on inadequate methodology," they wrote in the online journal PLoS ONE (www.plosone.org).

Led by Marco Del Giudice of Italy's University of Turin, the researchers took a 1993 survey of 10 000 men and women in the United States and re-crunched the numbers.

That survey, famous among psychologists as the Sixteen Personality Factor Questionnaire, quizzed its participants on such traits as warmth, dominance, sensitivity, vigilance, self-reliance, perfectionism and tension.

Comparing the overall profiles of men and women, and taking multiple traits into account, they discovered very large differences between the sexes - differences which had seemed to be smaller when each trait was looked at individually, without correction for measurement error.

"These are extremely large differences by psychological standards," wrote Del Giudice and colleagues Tom Booth and Paul Irwing of the University of Manchester in England.

By way of conclusion, they called for further research in order to build "a solid foundation for the scientific study of psychological sex differences and their biological and cultural origins."